ardinal Bernard F. Law and more than five bishops who worked for him have received subpoenas to appear before a state grand jury looking into possible criminal violations by church officials who supervised priests accused of sexually abusing children, according to people with knowledge of the investigation.

State troopers from the office of Attorney General Thomas F. Reilly delivered Law's subpoena to his Brighton residence last Friday, the same day that Law left for Washington. A day later, he flew from Washington to Rome.

The subpoenas, according to the sources, mark a pivotal phase in a secret, monthslong grand jury investigation convened by Reilly. The grand jury had previously demanded church records.

Reilly has said that his criminal investigation continues, even though he and other prosecutors have acknowledged that they have yet to find grounds to bring charges against Law and others alleged to have permitted sexual abusers to remain in positions where they continued to molest minors.

In addition to Law, the subpoenas have been issued for Bishop Thomas V. Daily of Brooklyn, N.Y., the nation's fifth-largest Catholic diocese; Bishop John B. McCormack of Manchester, N.H.; Archbishop Alfred C. Hughes of New Orleans; Bishop Robert J. Banks of Green Bay, Wis.; and Bishop William F. Murphy of Rockville Centre, N.Y.

At least one additional bishop and several priests who have assisted Law in dealing with the sexual abuse issue have also been subpoenaed, according to the people familiar with the grand jury inquiry. The identities of the other subpoena recipients could not be determined by the Globe last night.

In an interview Tuesday, Reilly refused to comment when he was asked whether he had subpoenaed Law. Yesterday, after the Globe learned about the multiple subpoenas, Ann Donlan, Reilly's spokeswoman, would only say that a ''comprehensive and active investigation'' continues.

Reilly declined to be interviewed yesterday, but on Tuesday, he accused the archdiocese of employing ''every tool and maneuver'' to impede his investigation, despite church officials' public pledges of cooperation. So far, Reilly said, the investigation has gathered evidence of what he called an elaborate and long-running scheme by church officials to cover up the crimes of priests.

Timothy P. O'Neill, a lawyer who represents Bishops Daily and Banks, said he could not say whether his clients have received subpoenas. But O'Neill said he thought that Reilly's comments, which were published yesterday by the Globe, were inappropriate.

''As a member of the bar, I am astonished that the attorney general would make substantive comments about an ongoing grand jury investigation,'' O'Neill, himself a former prosecutor, said last night.

It could not be determined when Law or any of the others are expected to testify. Although it is uncertain when Law is due to return from Rome, he is scheduled for two days of pretrial depositions, starting next Tuesday, in the civil suit brought by alleged victims of the Rev. Paul R. Shanley.

Law's personal attorney, J. Owen Todd, did not return calls.

Law himself remained out of view in the Vatican, where he has been since Sunday for meetings with Vatican officials about whether the Archdiocese of Boston should file for bankruptcy and whether he should resign as archbishop of Boston.

Law's aides in Boston had no comment on the cardinal's meetings in Rome.

As to the grand jury subpoena, testifying under oath about this issue will be nothing new for Law: So far, he has been deposed on 10 days since May 8.

But a grand jury appearance presents a different set of challenges for Law, the other bishops, and their lawyers.

Daniel I. Small, a former federal prosecutor and now a defense lawyer, said he saw no way for church attorneys to block the appearances by Law and the others.

If the grand jury is investigating possible criminal violations by church leaders, Small said, he would usually advise such a client to assert his Fifth Amendment rights and refuse to answer questions. ''From a strictly legal point of view, that advice is easy to give, if the client were anyone but Cardinal Law,'' Small said.

''The downside for a cardinal who invokes the Fifth Amendment would be enormous,'' Small said, noting the public perception of such claims by witnesses.

On the other hand, he said, it would be risky for Law to testify and rely on the grand jury process to keep his testimony secret. Prosecutors like Reilly, he said, can issue findings that include the grand jury testimony.

Reilly has said that he feels an obligation to report his findings to the public.

Reilly has never acknowledged the existence of the grand jury investigation, even after the Globe reported in June that the grand jury had been hearing evidence for several weeks. In April, Reilly said his office had not ruled out bringing criminal charges against the cardinal.

Prosecutors have investigated the possibility of indictments charging civil rights violations or conspiracy counts, though neither may apply. The issue most commonly raised is whether Law or the other bishops could be charged as accessories.

But legal specialists have said that such a charge would require proof that those to be indicted had intended that the priests under their supervision molest children. And, in most cases, the statute of limitations has long since expired.

Reilly's has been a major voice on the clergy sexual abuse scandal from the moment that disclosures began last Jan. 6. When Law apologized for his actions on Jan. 9, he said that all future allegations of abuse would be reported to authorities. Almost immediately, Reilly and several district attorneys publicly demanded that the church report all past allegations of abuse, and Law quickly agreed.

Initially, an agreement was struck for the church to voluntarily turn over files. But Reilly and other prosecutors soon complained publicly that the archdiocese was slow to provide the information. One prosecutor, Norfolk District Attorney William R. Keating, used grand jury subpoenas to force the handover of documents, according to law enforcement officials.

One person who knows about the subpoenas said that several archdiocesan officials, including other bishops, have already testified before the grand jury.

Walter Robinson can be reached at wrobinson@globe.com. Charles M. Sennott of the Globe Staff contributed to this report from Rome.